Hydraulic balancing of a cooling tower

For the chemical industry with its frequent exothermic reactions, the removal of process heat is of crucial importance. Cooling water, used for process heat dissipation, is cooled down in cooling towers where it is trickled, releasing the absorbed heat back into the ambient air.

In a common chemical plant, the cooling tower capacity proved to be inadequate, especially in warm months, which is why production had to be repeatedly cut back. For the responsible process engineers, this was the motivation to take a closer look at the cooling tower. Infrared imaging revealed the basic problem at first glance: While some trickling cells cooled the water effectively, it flowed through others without significant cooling. Obviously, the cooling tower lacked hydraulic balancing.

“A single one-day measuring service has allowed us to permanently increase the cooling capacity of the cooling tower by almost half and, accordingly, increase the capacity of our production facilities.“-- Andreas Drath, Reliability Engineer

During hydraulic balancing, it is essential that an equal amount of water passes through the individual cooling cells. However, how can this be achieved? In the individual case, each of the four cooling cells is fed by two supply lines (DN350). None of these lines is equipped with a flow meter. In order to find out how the quantities of water to be re-circulated are distributed among the individual lines, the operators turned to FLEXIM and commissioned a measuring service.

For the FLEXIM service engineer it was a routine job. With his portable, clamp-on FLUXUS F601 ultrasonic flow meter, he had recorded the actual status on all lines in a short amount of time. The measurements confirmed the assumption of a poor hydraulic balance: The measured quantities varied among the individual lines between 90 m³/h and 450 m³/h . Now it was a matter of equally distributing the flow rates by adjusting the valves appropriately. This task was also achieved effortlessly with the help of non-invasive flow measurement technology. All that was required was the cooperation of the FLEXIM service engineer, who again recorded the flow rates non-invasively on the eight lines, with an operating engineer who adjusted the valves accordingly. All work was carried out without any impairment of normal plant operation.

As a result, an enormous increase in performance was achieved by this simple measure. Instead of about 11 MW previously, the cooling tower now delivers about 16 MW of cooling capacity. Accordingly, the capacity of the production facility supplied by the cooling tower could be extended.

The cost and time required for a one-day measuring service is offset by an increase in production of around 1000 t/a - a prime example of how to tap significant potential for efficiency with minimal effort.

Advantages

Rapid recording of the flow rates on the eight supply lines to the cold cells without any impairment of normal plant operation

Easy and effective implementation of good hydraulic balancing based on empirical measurement data

The one-day measuring service taps a performance potential of ~ +50% and allows for production capacity to be increased by ~ 1000 t/a